Investigations will be undertaken to further define the molecular defect in the neurovisceral storage fucosidosis. Alpha-L-Fucosidase will be purified from tissues (liver, spleen, brain) from patients with fucosidosis by affinity and lectin chromatography, kinetically and immunochemically characterized and compared to the properties of the corresponding normal enzyme. A radioimmunoassay for alpha-L-fucosidase will be developed to be used in quantitating the amount of alpha-L-fucosidase-protein present in fucosidosis tissues. The role of sialic acid residues in the thermostability behavior of alpha-L-fucosidase (and its isoenzymes) will be investigated.